Network Card not acquiring IP address

After upgrading from RHEL 4 AS to RHEL 4 x86_64 the network card stop functioning. I get an error when tyring to acquire the DHCP IP Address that the cable is disconnected.
I tested the cable with another machine and it works fine. I removed and re installed the hardware? I'm able to ping to localhost (lo) and eth0 is active is just not communicating out.
THanks,